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Fourier Transform Infrared Spectroscopy. Gas sample is temperature controlled to allow comparison to previously measured spectra Interferometer path length is measured with a He-Ne laser, one intensity peak every 632.8nm of path length. Signal Processing and Analysis.
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Fourier Transform Infrared Spectroscopy • Gas sample is temperature controlled to allow comparison to previously measured spectra • Interferometer path length is measured with a He-Ne laser, one intensity peak every 632.8nm of path length
Signal Processing and Analysis • Measured transmission spectra is subtracted from a background measurement of IR-inactive gas to account for attenuation and non-linearity in the instrument. • Computer algorithm compares a set of reference spectra to find the combination of species and concentrations that best matches the measurement. H2O Reference Spectra Engine Exhaust Measurement